The present invention relates to network printing systems and more particularly, to network printing systems that provide for distributed transfer of data from a high level language into dots or pixels in a printer or imagesetter.
Typically network printing systems include at least one printer, at least one client computer, and at least one server distributed over the network. Networking systems may be of a LAN, WAN, token ring, ethernet, TCP/IP or other type. A client computer prepares data for a document or an image or a combination thereof and transmits the data over the network to a server that is linked to a desired printer. Various printers typically may have different printing capabilities. Where a print job requires specific capabilities, some network printing systems provide centralized and distributed management of the printing system so that the print job is routed to a printer that can handle the job.
A new print job typically has one or more electronically stored files along with print attributes for the files, The print attributes provide processing information for the files, typically in a job ticket or in conjunction with a job ticket.
Early printers received pages of data that were decomposable into a set number of lines, each having a preset number of character spaces. When printing, first the data was encoded using a Page Description Language (PDL), which determined the look of the printed page. Each command of the PDL corresponded to a feature of the printer. Such printers generally were called simple printers since simple PDLs were utilized.
Printers became more sophisticated, thus requiring more complex PDLs for controlling the printing. The increased complexity tended to cause development of printers that were more directly related to specific PDLs in accordance with the desired printing capabilities. Thus, applications then needed to be complex enough to accommodate a variety of printers, each of which had specific PDLs that it accommodated. Concomitant with the increased complexity of the applications, the cost of printers increased.
Before the advent of laser printers, the design of a PDL was straightforward. The hardware of the target printer had a limited number of capabilities, each capability having a command that controlled it. For example, Raster Image Processors (RIPs) were used to produce pixelmaps or bitmaps for higher languages for data written in the Postscript language. However, the hardware of a laser printer places dots onto the paper. In order to communicate the information for placing dots onto a full page at 9600 baud, i.e., about eight million bits, over fifteen minutes would be required. By putting a processor into the laser printer, the processor converted the data in PDL language to the eight million bits needed by the laser printer. However, since laser printers can print any combination of graphics, font styles and sizes, and since PDLs had typically had only limited instructions, new PDLs had to be developed. Some vendors developed common PDLs for particular printers, and some vendors just revised the whole set of PDLs. Programs for directing one printer often did not direct another printer properly. In particular, fonts needed to be designed with a bitmap for each size and orientation of each font. Data had to be converted to dots, typically using a RIP.
Complex languages were developed to allow descriptions of pages in addition to providing control of printers. Print image files such as a Postscript, Tagged Image File Format (TIFF), RIP, Portable Document Format (PDF) or Printer Control Language (PCL) file provided information on the location of the print image file within the network printing system and the location of the source file from which the print image file was generated to permit the user to modify the contents of the print image. The Postscript language is described in Adobe Systems Incorporated, Adobe PostScript Language Reference Manual, Addison-Wesley (2d ed., .COPYRIGHT. 1990). TIFF format is Tagged Image File format that is used for exchanging bitmapped images (generally scans) between applications. RIP format is Raster Image Processor format in which information is rasterized into a series of dots by an imagesetter or the like for transferring an image onto film or paper. PDF format is Portable Document Format that is available from Adobe Systems Incorporated at San Jose, Calif. PCL is a Printer Control Language available from Hewlett-Packard Company of Palo Alto, Calif. A Printer Control Language file typically specifies objects to be displayed and related information. For example, a PostScript object can include a pixel map defining a pattern of pixels to be displayed, the selected font, and/or font size or it can reference an outline curve that defines a shape to be marked in mathematical terms.
However, the use of the complex languages increased the cost of the printers that utilized such languages. Postscript, for example, divides the objects of a page into three categories: graphics, text and images, wherein graphics are represented mathematically as lines, text is represented by characters described as a mathematical outline, and images are represented as bitmaps. There is a need for methods, an image processing device, a computer network and a simple network printer wherein a simple printer is enabled to utilize the capabilities of the high-end printer or imaging system that has greater printing capabilities than the simple printer.